A single magnetic field is shown.
Answer:
<em>b. The current in the loop always flows in a counterclockwise direction.</em>
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Explanation:
When a magnet falls through a loop of wire, it induces an induced current on the loop of wire. This induced current is due to the motion of the magnet through the loop, which cause a change in the flux linkage of the magnet. According to Lenz law, the induced current acts in such a way as to repel the force or action that produces it. For this magnet, the only opposition possible is to stop its fall by inducing a like pole on the wire loop to repel its motion down. An induced current that flows counterclockwise in the wire loop has a polarity that is equivalent to a north pole on a magnet, and this will try to repel the motion of the magnet through the coil. Also, when the magnet goes pass the wire loop, this induced north pole will try to attract the south end of the magnet, all in a bid to stop its motion downwards.
Answer:
Explanation:
The velocity of a wave in a string is equal to:
v = √(T / (m/L))
where T is the tension and m/L is the mass per length.
To find the mass per length, we need to find the cross-sectional area of the thread.
A = πr² = π/4 d²
A = π (3.0×10⁻⁶ m)²
A = 2.83×10⁻¹¹ m²
So the mass per length is:
m/L = ρA
m/L = (1300 kg/m³) (2.83×10⁻¹¹ m²)
m/L = 3.68×10⁻⁸ kg/m
So the wave velocity is:
v = √(T / (m/L))
v = √(7.0×10⁻³ N / (3.68×10⁻⁸ kg/m))
v ≈ 440 m/s
The speed of sound in air at sea level is around 340 m/s. So the spider will feel the vibration in the thread before it hears the sound.
